The fire was first reported at 5pm yesterday afternoon.
A 25 year old man has been arrested in relation to a serious wildfire in County Down.
More than a hundred firefighters spent 10 hours tackling the blaze in the Hilltown area of the Mourne Mountains overnight.
It involved a large area of gorse and forestry and was first reported at around 5pm yesterday.
Difficult ground and high winds made it hard to contain however the fire was brought under control in the early hours of this morning.
Police have since arrested a man on suspicion of a number of offences, including arson.

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